Canadian Forest Service Publications

Répercussion des invasions de la tordeuse des bourgeons de l'épinette sur le sapin baumier et l'épinette blanche dans la réserve des Laurentides (Rapport d'étape). 1985. Blais, J.R. Service canadien des forêts, Centre de recherches forestières des Laurentides, Sainte-Foy (Québec). Rapport d'information LAU-X-68F. 16 p.

Year: 1985

Available from: Laurentian Forestry Centre

Catalog ID: 14359

Language: French

Series: Information Report (LFC - Québec)

CFS Availability: PDF (request by e-mail)

Abstract

The spruce budworm (Choristoneura fumiferana (Clem.)) outbreak that began in western Quebec in 1967 gradually progressed eastward and reached the Laurentian Reserve by 1972. In 1979, 37 study plots were established in the Laurentian Reserve to follow the progress of the mortality of balsam fir and white spruce. This is a report on the 1983 situation when only 6 percent of white spruce trees were dead while mortality of fir trees reached 54 percent. Mortality of balsam fir varied considerably between plots ranging from 0 to 100 percent. Mortality of fir trees in the 20 plots at elevations below 700 m reached 67 percent while in the 16 plots above 700 m it reached 37 percent. This difference was attributable to variations from year to year in defoliation between the two elevation zones. At elevations above 700 m defoliation decreased from 1978 to 1982; at elevations below 700 m defoliation remained high. Fir is the most common species at lower elevations and losses already amount to several million cubic metres in this zone. Because black spruce is the common species at higher elevations losses due to the infestation are not as consequential. There was no difference in mortality of fir between young and mature stands at higher elevations; at lower elevations mortality averaged 73 percent in mature and 51 percent in immature stands. The percentage loss in volume in relation to the percentage loss in stems was equal at lower elevations but was somewhat less at higher elevations. Many fir trees have reached the point of no return and mortality will progress at lower elevations irrespective of any future defoliation and will probably reach 85 percent in 1985. Progress of fir mortality at higher elevations will depend on insect numbers in this zone in the future. The majority of white spruce trees in both elevation zones will likely survive the outbreak.

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